1. Field of the Invention
The present invention relates to a semiconductor process, and more particularly, to a method for reducing defects of a deposited film.
2. Description of Related Art
Along with rapid progress of semiconductor technology, the dimensions of semiconductor devices are reduced and the integrity thereof promoted continuously to further advance the operating speed and performance of integrated circuits (ICs). As the demand for device integrity is raised, any tiny defects formed on a deposited film have to be considered to avoid a great impact on the operating speed and performance of the circuit.
Nowadays, many material layers are formed through chemical vapor disposition (CVD) in the presence of plasma, which uses a precursor containing organic molecules as a reactant gas. After a demanded material layer is formed on a substrate and reaches the pre-determined thickness, the source for the reactant gas is turned off to stop the deposition. The remaining reactant gas, however, would continue to dissociate and react on the surface of the material layer, thereby forming tiny defects thereon. To describe more in detail, after the disposition process using plasma, dangling bonds formed on the film surface may capture the residual radicals or ionic groups dissociated from the precursor, such that the radicals or ionic groups are prone to congregate and adhere in clusters on the surface of the material layer to form the particles with the size less than 0.05 μm, that is, the tiny defects. These tiny defects may be further exaggerated after forming a subsequent layer on the material layer in the follow-up step. The resultant defects with the size greater than 0.05 μm are formed on the surface of the subsequent layer, and thereby can be detected. As a result, such defects may seriously impact the subsequent process and product reliability.